Using Python new style string formatting in Sage

[Zoresvit]

Is there a way to use new Python string formatting in Sage without disabling the preparser?

For now I get the following:

sage: "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/home/zoresvit/devel/ciphering/algebraic/<ipython console> in <module>()
ValueError: Unknown format code 'd' for object of type 'str'

If the preparser is off, everything works:

sage: preparser(False)                                                 
sage: "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'

I'm using Sage 4.8:

$ sage --version
Sage Version 4.8, Release Date: 2012-01-20
$ sage -python
Python 2.6.4 (r264, Jan 20 2012, 00:16:31) 
[GCC 4.4.3] on linux2

Thanks.

[Jason Grout]

On 3/7/12 5:50 AM, Zoresvit wrote:
> Is there a way to use new Python string formatting

> <http://docs.python.org/library/string.html> in Sage without disabling

> the preparser?
>
> For now I get the following:
>
> sage: "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
> ---------------------------------------------------------------------------
> ValueError Traceback (most recent call last)
> /home/zoresvit/devel/ciphering/algebraic/<ipython console> in <module>()
> ValueError: Unknown format code 'd' for object of type 'str'
>
>
> If the preparser is off, everything works:
>
> sage: preparser(False)
> sage: "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
> 'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'
>

The problem is that apparently format doesn't accept Integers:

sage: "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(int(42))

'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'

sage: "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin:

{0:#b}".format(Integer(42))

---------------------------------------------------------------------------
ValueError Traceback (most recent call last)

/Users/grout/jason/drake/linear-algebra/Exams/<ipython console> in
<module>()

ValueError: Unknown format code 'd' for object of type 'str'

Thanks,

Jason

[Zoresvit]

Thanks a lot! Always forgetting Sage has its own type for integers. Some automatic coersion would help a lot in such situation.

[Dima Pasechnik]

On 2012-03-25, Zoresvit <zore...@gmail.com> wrote:
> ------=_Part_2975_1350727.1332636811930
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: quoted-printable
>
> Thanks a lot! Always forgetting Sage has its own type for integers. Some=20

> automatic coersion would help a lot in such situation.

Given that not every Integer fits into an int, this would be asking for
trouble. Rather, Sage should specify its own format for Integer, etc.

[Nils Bruin]

 
On Saturday, March 24, 2012 11:01:15 PM UTC-7, Dima Pasechnik wrote:

Given that not every Integer fits into an int, this would be asking for
trouble. Rather, Sage should specify its own format for Integer, etc.

true, but Python handles the overflow gracefully by returning a long instead, and in Python 3 there is no int/long dichotomy on the language level any more. It's probably convenient to put a __format__ method on Integer, but its implementation could be very simple:

def __format__(self,*args,**kwargs):
    return int(self).__format__(*args,**kwargs)

If this leads to performance issues, one could consider writing a custom version that accepts the python format mini-language.

[Nils Bruin]

patch up at http://trac.sagemath.org/sage_trac/ticket/12788